Error while lifting. about llvm-mctoll

[bharadwajy]

Thanks. But i am still getting the same error after that.

``llvm-mctoll: /data/llvm-project/llvm/tools/llvm-mctoll/X86/X86MachineInstructionRaiserUtils.cpp:1531: llvm::Function* llvm::mctoll::X86MachineInstructionRaiser::getTargetFunctionAtPLTOffset(const llvm::MachineInstr&, uint64_t): Assertion `(GotPltReloc->getType() == ELF::R_X86_64_JUMP_SLOT) && "Unexpected relocation type for PLT jmp instruction"' failed.

It appears that you need to pull the llvm-mctoll repo as that line has been part of the change I pushed - see here. Rebuild llvm-mctoll once you update your llvm-mctoll repo.

I have verified that the change works using the sclang binary you provided earlier before I pushed.

[bharadwajy]

Thanks so much. It worked. I was just pulling llvm project instead of llvm-mctoll. But i am getting this:

Unknown prototype for function : strcmp
Use -I </full/path/to/file>, where /full/path/to/file declares its prototype

Do we need the include file to get the llvm IR? If we actually need to put it, does that mean some portion of source is needed to lift binary to IR? and when using the command "llvm-mctoll -d " yield the result in the interface itself?

You do not need any portion of the source file. You will need to provide the prototypes of externally linked functions (such as strcmp) for llvm-mctoll to help the process of raising as described here. llvm-mctoll cannot figure out the prototypes of externally linked functions just using the binary.

For example, here is a portion of the file I created with external (i.e., glibc) function prototypes to ensure that the tool makes progress beyond the assertion fix I made while raising your binary.

$ cat myinclude.h
#include <stddef.h>

int strcmp(const char *s1, const char *s2);
int strncmp(const char *s1, const char *s2, size_t n);
char *strcpy(char *dest, const char *src);
size_t strlen(const char *s);
char *strndup(const char *s, size_t n);
char *strdup(const char *s);

$ llvm-mctoll -d -I /full/path/to/myinclude.h sclang

Please note that I have not added all the necessary prototypes. Please add any additional prototypes to check if your sclang binary can be raised by llvm-mctoll.

[bharadwajy]

Thanks for your interest in the project.

I have pushed a change to relax the assertion to handle the relocation type R_X86_64_GLOB_DAT.

Let me know if that helps.

[anzosasuke]

Thanks. But i am still getting the same error after that.

``llvm-mctoll: /data/llvm-project/llvm/tools/llvm-mctoll/X86/X86MachineInstructionRaiserUtils.cpp:1531: llvm::Function* llvm::mctoll::X86MachineInstructionRaiser::getTargetFunctionAtPLTOffset(const llvm::MachineInstr&, uint64_t): Assertion `(GotPltReloc->getType() == ELF::R_X86_64_JUMP_SLOT) && "Unexpected relocation type for PLT jmp instruction"' failed.

*** Please submit an issue at https://github.com/microsoft/llvm-mctoll
*** along with a back trace and a reproducer, if possible.
Stack dump:
0. Program arguments: ./llvm-mctoll -d sclang
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var LLVM_SYMBOLIZER_PATH to point to it):
0 llvm-mctoll 0x0000558dac9fca56
1 llvm-mctoll 0x0000558dac9fa43e
2 libc.so.6 0x00007f59c9caf520
3 libc.so.6 0x00007f59c9d03a7c pthread_kill + 300
4 libc.so.6 0x00007f59c9caf476 raise + 22
5 libc.so.6 0x00007f59c9c957f3 abort + 211
6 libc.so.6 0x00007f59c9c9571b
7 libc.so.6 0x00007f59c9ca6e96
8 llvm-mctoll 0x0000558dad04c36b
9 llvm-mctoll 0x0000558dad063c6f
10 llvm-mctoll 0x0000558dad02c3cd
11 llvm-mctoll 0x0000558dac19f51d
12 llvm-mctoll 0x0000558dac13f942
13 libc.so.6 0x00007f59c9c96d90
14 libc.so.6 0x00007f59c9c96e40 __libc_start_main + 128
15 llvm-mctoll 0x0000558dac18d1c5
Aborted (core dumped)

I have attached the file at the top if you want to recreate.

[anzosasuke]

Thanks so much. It worked. I was just pulling llvm project instead of llvm-mctoll. But i am getting this:

Unknown prototype for function : strcmp
Use -I </full/path/to/file>, where /full/path/to/file declares its prototype

Do we need the include file to get the llvm IR? If we actually need to put it, does that mean some portion of source is needed to lift binary to IR? and when using the command "llvm-mctoll -d " yield the result in the interface itself?

[anzosasuke]

Got it. Thanks so much.